1. Field of the Invention
The invention relates generally to an improved pinion gear carrier for use in a rotary drill head and particularly to a pinion gear carrier which may be easily and quickly removed from the drill head casing and which is constructed so that if a seal in the hydraulic drive motor for the pinion gear fails, the pressurized fluid from the hydraulic motor will be released to atmosphere and hence will not blow seals located in the drill head casing or the pinion carrier housing.
2. Description of the Prior Art
Both percussion and nonpercussion rotary drills are used in rock drilling, and the drill steel which carries the bit is supported in a rotary member in the drill head. The lower end of the rotary member is attached to a ring gear, and a socket like portion is formed at the upper end to support the drill steel. The ring gear is normally driven by a pinion gear which is driven by a hydraulic drive motor. The hydraulic motor has a rotatable drive shaft which is nonrotatably connected to the pinion gear so that the hydraulic drive motor rotates the pinion gear to rotate the ring gear and the member which carries the drill steel. In prior art drill heads, the pinion gear is located inside of the drill head casing and the hydraulic drive motor which drives the pinion gear is located outside of the housing. The motor drive shaft extends through bearings and seals located in the drill head casing. In this arrangement, when either the hydraulic drive motor or the pinion gear fail, it is necessary to tear down the drill head in order to replace either of them, and this is both time consuming and expensive. Additionally, if the seals in the casing of a prior art drill head fail, dirt and rock dust enter the drill head casing and this causes bearing failure. An example of a prior art drill head is shown in U.S. Pat. No. 3,190,369.